Are you aerobic?

CrossFit is known for short workouts that leave you breathless. "Go Long" to become more fit and eventually go faster.
Jake Crandall
February 25, 2022
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The Greatest Exercise You’re Not Doing Enough

TLDR: Don't focus on 5-12 minute WODs that bury you and leave you on your back for 10 grasping for air. "Go Long". Ride a bike, walk, hike, etc for 60 minutes plus 2 times a week to build your aerobic base. Believe it or not, your soreness will diminish and you'll get even faster when intensity is needed. At Okie CrossFit in Tulsa, we program both intense days and longer "cardio" days that focus solely on building our aerobic engines. We also have 24/7 access at both locations so our members can come in and bike, row, ski, or run on a treadmill. If you're in the Tulsa area and want to try a FREE WEEK of Tulsa's best CrossFit Gyms (2 locations) use this link. If not, use the information below to build your aerobic work capacity.

Do I have your attention?!?! Good.

Whether you’ve been doing CrossFit for 1 month or 3+ years, you’ve been heading to your “Box” several times a week pretty consistently and have made pretty good progress. You’ve gained muscle, lost fat and improved your cardiovascular-respiratory fitness. But then all the sudden, the low hanging fruit is all picked from the tree and the dreaded plateau is hit.  Sometimes people plateau in 3 months, sometimes 3 years, but it is inevitable to happen.

You give it all in your WODs, and they leave you gasping for air and half dead on the floor. Most people think of this feeling as the one that will get them better week after week, month after month, and year after year.  But the truth is, when you’ve hit a plateau, this “feeling” may be what is stalling your progress or even possibly starting you to regress.

You’ve tried everything: lifting more to get stronger, doing more power work to get faster, even doing more “metabolic conditioning” work to get faster in WODs. None of it has seemed to help. You start doing any WOD you see on Instagram  or running miles each day outside of your CrossFit classes only to find yourself “gassing out” early and unable to maintain power output as the days and workouts go on.

So what happened?

You’ve probably neglected the one area of fitness that would actually help your performance – your aerobic system. In my experience, most CrossFitters (beginner to 3 + years) have a sub average aerobic system compared to their strength and power capabilities.

This happens because the CrossFit community (all the stuff you see on Instagram) tends to focus on building the aerobic system through crazy WODs, essentially high intensity interval training, and not dedicated aerobic work. While this will improve the “conditioning” of beginners and those with poor aerobic systems/fitness to begin with, eventually using strategies like the famed Tabata (8 rounds of :20 work / :10 rest ), 21-15-9, etc… will stop working and may actually be what’s holding back your performance.

Energy Systems 101

The human body is amazing and uses the compound adenosine triphosphate (ATP) for cellular metabolism. Basically, anything a cell needs to do, it needs ATP for the energy to do it. The body produces ATP through three different pathways:

  1. Alactic Anaerobic (ATP-CP) – This is the shortest (activity lasting 1-2 seconds), fastest acting, and most easily depleted. Think of this as a set of strength work.
  2. Lactic Anaerobic – This is what most people refer to as “anaerobic” training. Anaerobic is Greek for “without Oxygen”.  This training lasts from 60-90 seconds.  During Anaerobic activity, the body relies on glycogen for fuel.  Think of this as bike sprints, sled pushes, work / rest work, etc...
  3. Aerobic (oxidative) – Aerobic is Greek for “with Oxygen”.  This is the primary energy system we use the vast majority of the time. It is the dominant system, resting after 90 seconds of activity.  During aerobic activity, the body is using fat as fuel.  

Keep in mind that all three systems are actively producing energy constantly. The contribution each one makes varies greatly based on your age and the duration of an activity – not the intensity.

The Aerobic System

Your aerobic system is how the body produces the most energy (ATP) per cycle. During aerobic metabolism one molecule of glucose yields 36 ATP, compared to only 2 during anaerobic metabolism (when you run out of O2 (anaerobic), you only net 2 ATP from 1 molecule of glucose). The only drawback to aerobic metabolism is a slower process than the other two. While it takes some time to churn out those ATP, you can use the aerobic system literally for hours without fatiguing excessively or “gassing out”.  Example:  Which will leave you absolutely destroyed? 1 sled push every minute for 30 minutes (anaerobic) or 30 minutes on a bike at a leisurely pace (aerobic).

The ATP-CP and Lactic Anaerobic systems deplete quickly. When this happens fatigue sets in. You can observe this in marathon runners who perform continuously for hours primarily using the aerobic system, while sprinters are completely fatigued at the end of a 10 second 100 meter sprint where the ATP-CP system is dominant.

The aerobic system has some other important qualities to remember:

This last point is important because stressful, high intensity, or fatiguing training initiates the fight or flight system. The aerobic system helps to manage the response to the stress. While we want the fight or flight system to start up, we do not want a larger response than is needed. An overly larger sympathetic response will only cause the heart rate to skyrocket and remain elevated. This will initiate the Lactic Anaerobic system, fatiguing you sooner than necessary, and keep you  in a (sympathetic) state and not allow you to recover properly. A good aerobic system will help properly manage the response to a stressor. In this case, exercise.  A good aerobic system also burns fat faster when combined with weightlifting and WODs.

Mitochondria: Where the ATP is Made and the Magic Happens

Often referred to as the powerhouse of the cell. This is where aerobic metabolism takes place. The more aerobic training you do, the more mitochondria you build. The more anaerobic (lactic) training you do, the slower you build your mitochondrial reserves. If you remember nothing else, please remember this.  Building more mitochondria is the key to producing more energy (ATP) and burning more fat.

Anaerobic Threshold: Hitting the Sewer Line

Everyone has reached that point where fatigue starts to rapidly accumulate. Your legs, lungs, and muscles start to burn – and you’re really hating life. At this point, you’ve passed your anaerobic threshold: the point at which we can no longer clear the waste products (hydrogen ions) from ATP production. An acidic environment is created in the cells and fatigue starts to accumulate rapidly. Training in this area can be very valuable. There are enzymes, phosphofructokinase (PFK) and phosphorylase produced that will help you resist fatiguing when training here.  A great analogy for passing your anaerobic threshold is imagine putting a pool in your backyard.  You’re in a hurry to swim, so you don’t check for underground pipes.  You hit a sewage line while digging and your yard and your plans to go swimming go to crap.  Literally.

It feels terrible while you’re doing it, but it’s also very physically and mentally draining. Thankfully, after 6-8 weeks you’ve maxed out your possible improvements. Keep in mind that while you’re doing this type of training you’re actively destroying mitochondria and limiting your overall ATP potential. The longer you train, the more you stress this system, and end up destroying even more mitochondria.  That’s ok though.  We’ll get to how to fix that later.

Repeated Sprint Ability

Most WODs are nothing more than a series of sprints with short rest periods. You work very hard for a bit (pacing the best you can) but find yourself taking 10-20 second breaks when needed.  Repeating this process for however long the WOD is. While this is a misrepresentation of what CrossFit wanted for a conditioning program, it’s what CrossFit has become.  Again, that’s ok and we can fix it.

Framing this in the context of energy system training, it seems like WODs are nothing more than primarily Lactic Anaerobic training followed by a short rest period, repeated over a certain distance of times or reps. Because of this we should focus on training the Lactic (LA) system. However, the research on repeated sprint ability has shown us that this isn’t the case. Remember: all energy systems are interrelated and turned on constantly, only the contribution changes.

Why You “Gas Out” During WODs

Besides the fact that WODs are really hard, you’ve only been training your lactic anaerobic system.

For the first few efforts in a WOD, before your heart rate elevates and exceeds your lactate threshold, you’re able to produce power. But once you pass your lactate threshold and accumulate fatigue, your aerobic system isn’t kicking in enough to help you recover and maintain your power output. You literally sprint /rest / repeat.  Resting more than sprinting.  LOL. The consequence is that you MUST slow down, lengthen rest periods, lower power output, or even stop all together.  You’ve “gassed out”.

Before you get into CrossFit, your anaerobic training (LA)  ceiling is very low. You pick a ton of low hanging fruit early in your CrossFit journey and enter into anaerobic metabolism early and never get out of it.  Again, it’s ok.  We’re going to fix that.

What do you do to Become Aerobic and Fix This:

This doesn’t mean you need to start running 5 miles a day. You could, but nothing would turn you off of a training program faster.  You’d also wreck your body.

The most effective form of aerobic training is cardiac output training. This will help build both a larger base of aerobic conditioning, as well as replenish (possibly in a surplus) mitochondria to produce ATP.

One way is to go on a varied walk (not hiking a mountain, but also not a flat track).  Wear a heart monitor or be ready to take your own pulse.  The goal is to stay between 120-150 beats per minute for 30 - 45minutes.  You can do this with your kids on an evening walk with the family (kids on bikes).  If you need to get your heart rate up, do 3 burpees or 8 squats.  Just keep your HR in that zone.

Another way is to walk / run.  Again, keeping your HR between 120-150 beats per minute for 30 - 45 minutes. 

The heart is a dumb muscle and only responds to the needs of the body. The type of exercise doesn’t matter. As long as it lasts for at least 30 minutes and the heart rate stays between 120-150bpm, you’re good to go.  Don’t overreach with the heart rate.  If you find yourself getting and staying above 150 bpm, walk slower.

The only rules you need to follow are:

  1. Heart rate of 120-150 beats per minute. 
  2. 30-45 continuous minutes.


Ways to do this outside the Gym

Yes, you still need your weightlifting and heavy (anaerobic work) inside the gym, but you also need to build your aerobic base.  How can you do this?  Walk.  Daily.  Set a crazy step goal (12-15,000 or even 20,000 steps per day) and get it.  Walk during lunch, Take short breaks at work and walk a bit.  After the workout at the gym, walk 4-800 meters for a cool down.  Towards the end of the day, go outside and walk until you hit your goal.  It’s simple.  

The bottom line

Chances are you started CrossFit to look great in a bathing suit.  Whether that is still your goal or you want to compete at a high level, you need to be highly aerobic.  The long slow work burns up fat and helps prepare you more for the short heavy work.  At Okie CrossFit in Tulsa, we program both intense days and longer "cardio" days that focus solely on building our aerobic engines. We also have 24/7 access at both locations so our members can come in and bike, row, ski, or run on a treadmill. If you're in the Tulsa area and want to try a FREE WEEK of Tulsa's best CrossFit Gyms (2 locations) use this link. If not, use the information above to build your aerobic work capacity.

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